Yes, he just would have to explain peolpe why conservative policies since 1980 caused a catastrophical and useless crusade and an economical crisis due to a blind "laisser-faire" ideology. In synthesis, why conservatism ruined America. You're right, nothing more simple !
On that particular count, actually, John McCain had the same problems as a far right Republican would have had. (And Obama hardly represented change, anyhow. 
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Only because he chose to compromise himself with the conservative religious right : his pick of Sarah Palin meant exactly that. And it was a dramatic erroc : had McCain not done this, he could have come much more close to Obama. But GOP os today the prisoner of a disastrous strategy, to mobilise an hypothetical "conservative grass roots". It worked once, in 2004, but definiteli disgusted indipendent voters.
Actually that is not true at all. Sarah Palin closed McCain closer to Obama then he was before the pick. The economic collapse in September finished McCain.
I think there's a lot of ambiguity over Palin's later effect in light of the economic collapse that followed during it, but considering her introduction was a lot better than her follow-up, I don't think you can make a concrete conclusion either way. I tend to think that it hurt the "brand" long-term, but I can't really prove it either way.
Her approval ratings did decline, IIRC, to the point where they were a drag on McCain and the ticket but maybe I mis-remember.
McCain campaigned well enough early. Obama simply ran the best Presidential campaign that I have seen in my lifetime, and that includes Presidential campaigns as far back as 1964 -- blow-outs and close ones alike.
There is no such thing as a normal campaign year. Political concerns can and do change rapidly, and political styles matter greatly. So do opportunities. As I see it, McCain did very well considering that he was following an incumbent President within his own Party -- an incumbent heavily discredited. He didn't get control of the GOP apparatus; it controlled the agenda. The people who supported Dubya still controlled the agenda of the GOP.
He was close in popular vote until the economic meltdown of the autumn of 2008 -- and he didn't have a clue on how to meet it. To avoid losing he had to make gambles with high payoffs if successful but defeat if unsuccessful. McCain made quixotic efforts to win Pennsylvania, Wisconsin, Michigan, and New Hampshire -- and those cost him Ohio, Florida, Indiana, and North Carolina. He had no choice; he was losing Virginia, Nevada, and Colorado.
Sarah Palin was a huge blunder, but I am not sure that she was his first choice. The Party leadership probably foisted her upon him in the expectation that she would win over people who might have supported Hillary Clinton in the primaries.
Political geography doomed McCain unless he ran a very effective campaign against a weak opponent. Seventeen states and the District of Columbia hadn't voted for any Republican nominee for President since at least 1988.. and after eight years of a President who had done nothing to win those states over, they went for the Democrat by double-digit margins. None were close! Those states combine for 248 electoral votes -- 22 short of victory. Then add New Hampshire, Iowa, and New Mexico, states which had voted only once for a Republican nominee for President since 1988 -- and it's only 6 electoral votes away from a Democratic victory outright. Neither of those three states was close in 2008. Nevada ensured a tie -- that would have been decided in the House of Representatives to the obvious benefit of Obama.
A moderate Republican with a moderate GOP might have cut into the so-called "Blue Firewall" and forced Obama to make some quixotic gambles -- like trying to pick off Texas as Pennsylvania and Michigan slipped away -- but however McCain claimed to be a moderate, the GOP wasn't. Then came the economic catastrophe that voters attributed to the GOP: the stock market collapse that scared everyone.
